The present invention generally relates to a connection between conduits. More specifically, the present invention relates to a connection for a conduit that carries a heat exchange medium or vacuum into one or more fluted cylinders in an apparatus for producing corrugated paperboard. Furthermore, the present invention specifically relates to a conduit connection in relation to cylinder cassettes configured for frequent changeover.
In known processes for corrugated cardboard or paperboard, a first sheet of paper is corrugated by rolling it between first and second intermeshing fluted cylinders. After the sheet has been corrugated, it is then retained in the flutes of the second cylinder as the cylinder continues to rotate. A gluing cylinder applies glue along the crests of the corrugated sheet as it is held in the flutes. A cover sheet is then applied to the corrugated sheet by pressing the cover sheet to the glued crests of the corrugated sheet by a pressure cylinder, which coacts with the second fluted cylinder.
The above described process is known as "single facing," as it results in a corrugated board having only one flat side. With a subsequent step, "double facing" is achieved by applying another sheet to the single-faced sheet so that both sides of the corrugated sheet are covered.
In order to provide effective and efficient gluing during a "single-facing" process, the fluted cylinders, and sometimes the pressure cylinder, are heated. It is know to heat such cylinders by circulating pressurized, superheated steam within an interior cavity of such a cylinder. Condensation from the heat exchange medium, such as steam, is withdrawn from the cavity.
Also, it is known to apply a vacuum through small holes in the surface of a fluted cylinder in order to retain the corrugated sheet within the flutes as the cover sheet is being pressed to contact therewith by the pressure cylinder. For instance, such devices are disclosed in U.S. Pat. No. 4,381,212, whose disclosure is incorporated by reference thereto, German Patent DE 28 23 674, and U.S. Pat. No. 4,917,664.
U.S. Pat. No. 4,917,664, whose disclosure is incorporated by reference thereto and which claims priority from the application resulting in French patent document 2,622,145, relates to a fluted cylinder having an inner chamber which is permanently linked to a vacuum source and has a series of radial suction apertures which open on a peripheral surface of the cylinder. Furthermore, the cylinder includes a series of axial channels having a permanent circulation of steam which enters and leaves through two coaxial channels arranged on the supporting shaft. Typically, prior art devices have conduits which are fitted in permanent or semi-permanent manner.
Depending on the type of a cardboard product to be produced, a particular corrugation configuration must be provided. Therefore, it is desirable to quickly exchange fluted cylinders in a "single-facing" apparatus for cylinders having a different size or shape corresponding to the desired corrugation. In order to exchange cylinders quickly, it is known to provide a single cassette which houses a pair of fluted cylinders with their bearings and driving motors. Such cassettes are configured to be inserted and received by a frame of a machine which performs other steps such as feeding paper to the cassette, etc. For such a cassette, it is known to provide a cooperative system of rails and rollers between a cassette carriage and the frame so that the cassette can be easily inserted and removed. It is further known to provide a machine which utilizes multiple cassettes. A first cassette can be fitted in an upper space of the machine, having a second cassette positioned below. A mechanism provides for lowering the second cassette in an orthogonal direction.
To change cassettes, it is necessary to disconnect and reconnect the conduits which supply and return steam or vacuum pressure to the side of a cassette adjacent trunnion bearings for the cylinders. Because such connections are traditionally semi-permanent, connecting each conduit involves the insertion of a flange in a bushing and tightening a nut. This can be tedious work, resulting in a slow exchange of cassettes and lost production time.